I have the code above in DBaction3-3.php, it will be reached from http://dot.kr/x-test/todbAction3-3.php.The result of it is "select id from myTable1 where title='' instead of "select id from myTable1 where title='title1' "?

Which sort of solves your second problem because referring to $title inside a string is a lot simpler than referring to $_POST['title'];

But, FYI if you ever do need to use an associative array value in a string you have these options:

/* no single quotes required around 'name'
because the string is wrapped in double quotes
and the variable will be parsed */
$myString = "Hello $_POST[name], how are you?";
/* single quotes required when using curly
brackets to isolate the variable */
$myString = "Hello {$_POST['name']}, how are you?";
/* concatenate */
$myString = 'Hello ' . $_POST['name'] . ', how are you?';

jotJoon you still have a dollar sign in front of $myVar near where you have highlighted POST in red. You even quoted my post where I said not to use $myVar Like Kalon and I said you need to remove that dollar sign. You're referring to an array key, not a variable.